1. Field of the Invention
The present invention relates to a fluid ejection apparatus, and in particular to a fluid ejection apparatus that generates a virtual valve.
2. Description of the Related Art
Referring to FIG. 1, U.S. Pat. No. 6,102,530 discloses an inkjet device 1 which can generate a virtual valve. Two heaters 20, 22 are disposed beside an orifice 18. Ink 26 flows into a chamber 14 through a manifold 16.
Referring to FIG. 2A and FIG. 2B, the inkjet device 1 ejects the ink 26 using the heating speed difference between the heaters 20 and 22. Namely, the heater 20 reaches a predetermined temperature to vaporize the ink 26 to form a bubble 30 thereunder. As the size increases, the bubble 30 serves as a virtual valve to 20 isolate the chamber 14 from the manifold 16. The heater 22 then reaches the predetermined temperature required to vaporize the ink 26 to form another bubble 32 thereunder. The two bubbles 30 and 32 push the ink 26 to eject the ink 26 via the orifice 18.
Accordingly, the heaters 20 and 22 have different resistances, such that the heaters 20 and 22 have different heating speeds. The bubbles 30 and 32 formed thereunder have different forming speeds to generate the virtual valve. Thus, when the inkjet device 1 ejects the ink 26, the crosstalk therein is prevented and satellite ink droplets are reduced.
Nevertheless, since the resistances of the heaters 20 and 22 in the inkjet device 1 are different, the sizes of the heaters 20 and 22 must be accurately controlled to match the geometric shape of the chamber 14 and the orifice 18. Otherwise, the ink 26 in the chamber 14 is ejected obliquely or not ejected. Thus, the design of the inkjet device 1 is complex and the manufacture thereof is difficult.
Hence, there is a need to provide a fluid ejection apparatus to allow the ink therein to eject vertically and stably.